You will see thousands of rom files, but they are not copies of diskettes, but of programs, usually games.
You cannot make physical floppy disks from a rom file and you cannot change and save them.
I see more and more rom files, even made from small basic programs, but you cannot change or modify them.
You can also create dsk files with programs and files from other dsk files or from a physical floppy disk.
This way you can create a dsk file with your best games and save it to a real floppy disk for your MSX or for use with RuMSX ofcourse.
This works just as easily as with real floppy disks.
Making a diskette with several small ROM files of your favorite games is much, much more difficult.
Of course preference is given to dsk files over rom files.
ROM files are very suitable for large games that take up an entire diskette or even several diskettes anyway.
For small files and games, you prefer to use dsk files.
Making rom files from small games and even basic programs is just idiotic.
Some believe that rom files are easier, because they (often) start automatically.
But that depends on the creator of the disk image, the dsk file.
I almost only have floppies that start automatically, so also the dsk files made from them start when you click on them.
The files in a dsk file are easy to adjust and you can make them start up automatically.
But you can also put pokes and peeks in that charger for extra lives for example.
If a dsk file does not start, it is up to its creator.
You can also create non-booting rom files.
Rom files are nice for very large games, small ones are much better in a dsk file, which you can also put on a physical diskette.
Making dsk files is much easier than making rom files that can also be used on an MSX
Years ago I made a menu that makes it easy to delete, copy and rename files.
You can use it to make and use diskettes with ten, twenty or more games.
I have not yet seen those possibilities with a rom file.
I am now translating that menu program and it will follow.
Creating a dsk file with an empty diskette to write or copy to is child's play for RuMSX.
Create a dsk file from a physical MSX diskette with RuMSX
Format a floppy disk on PC in just a few minutes with RuMSX and copy Nemesis 1 from dsk to it.